Numerical calculation and field application of gas emission from coal wall in dynamic mining face

In order to accurately predict and calculate the gas emission from the coal wall of the working face during the dynamic mining period,No. 22051 fully-mechanized mining face of Chaohua Coal Mine was taken as the research object to establish the multi-component gas content pressure model of coal seam. Considering the advancing speed of the working face and the change of coal seam permeability under the influence of mining, and by introducing the moving coordinate system and the coal seam permeability distribution model in front of the working face under the action of mining, the simplified calculation model of gas emission from the coal wall during the dynamic pushover mining was established, and the corresponding calculation program was compiled by the finite difference method. Based on the gas balance equation and air volume balance equation, a mathematical model for the calculation of gas emission from the working face was established, combined with the on-site gas volume measurement method at the working face, and the gas emission from the coal wall of the working face was measured.The results of numerical simulation and actual measurement of gas emission from the coal wall of No.22051 working face were compared and analyzed. The results show that in the numerical model of gas emission from the coal wall of the working face, the parameter value of the average daily advancing speed of the coal face should be calculated from the actual advancing degree of the coal face within 25～35 days.The mining footage condition of the working face has an important effect on the gas seepage and migration in the coal seam in front of the coal wall of the working face. Under the current mining conditions and coal seam gas occurrence and seepage conditions, the amount of gas emission from the coal wall of the coal face depended on the mining footage within the time range of 25～35 days, and there were obvious time accumulation and delay effects in the gas emission from the coal wall of the coal face.